Are you sure it's a bruise and not a venous supply area? Does it stay the same size or has it gotten larger as time progressed? Perhaps with your worry over the area, and palpating it for tenderness, you have caused a bruise to occur with just checking on it? If it has not gotten any bigger, and there is no pain that radiates or has a streaking from it...I'd simply try to get it to absorb with some hot packs to that area. But since you don't describe any initial injury to that area, you will definitely need to have the MD take a look at it, and possibly order some xray or doppler tests to check for clotting. Don't rub or palpate that area when applying the hot packs, just let it sit for no longer than 20 minutes at a time and always place something between the pack and your leg to prevent any burning of the skin. Good luck!
*the bruise was NOT on my leg before, it has appeared this week